This invention relates to industrial type heating devices such as heat treating or sintering furnaces, ovens or kilns operating with a controlled gaseous atmosphere therein, and comprises a novel construction therefor and method of operating such a heating unit. The furnace or oven, etc., construction, and method of operation of this invention, provide substantial savings in the energy or power needs to effectively heat and operate controlled atmosphere heating devices.
Heat treating, sintering and the like furnaces and ovens have traditionally been designed and constructed according to one of two established categories or systems. One type of furnace operates with the particular gas of the controlled atmosphere within the heating chamber simply extending or permeating throughout the entire cross-section of the complete unit, including occupying any areas beyond or external to the refractory walls providing the hot face of and defining the heating or sintering chamber area and reaching to the outer furnace housing which is generally of a substantially gas tight construction.
The other type of furnace or oven for controlled atmosphere service includes a gas tight muffle or shroud unit to contain and isolate the particular atmospheric gas within its confines defining the heating or sintering chamber area. The space external to the muffle or shroud unit, which usually includes the thermal insulation and heating means or elements, appropriately has an atmosphere of a gas that is compatable with any components such as the insulation and heating means located in the outer portions of a muffle furnace, and therefore can be different from the atmosphere within the muffle. Furnaces of this latter type comprising muffles or gas tight isolating enclosures are illustrated in U.S. Pat. Nos. 1,472,401 and 2,064,532.
Muffle type furnaces or ovens, however, are relatively expensive to construct and they frequently encounter difficulties with respect to their reliability under certain operating conditions, such as reaching and maintaining very high temperature levels that are often required for many contemporary manufacturing procedures.